Rotary mixing machine



April 17, 1928. 1,666,324

J. F. BURN ET AL ROTARY MIXING MACflINE Filed larch 24. 1927 2 Sheets-Sheet 1 April 17, 1928.

J. F. BURN ET AL ROTARY MIXING MACHINE Filed March 24. 1927 2 Sheets-Sheet 2 v of showing the mterior of Patented Apr. 17, 1928.

JOHN FAULDER BUBN,

or rionnon, m) Jo n: STUART LANCASTER, or 'wsawrcx,

"ENGLAND.

.ROTARYiMIXING 'MACHIN E.

Application filed This invention relates to rotary mixing machines, and more particularly-to:machines for mixing concrete or similar material.

It is common to employ a :receptacle, known as a drum, (for this purpose :the'sides of which taper frusto-conically to a mouth of smaller diameter, the bottom resembling a basin withcurved surfaces having aieentral portion adapted :to form a bearing forssupporting it rotatably upon an axle, inclined so as to cause the material contained therein to fall back repeatedly on to :the curved bottom, and-the drum'being tiltable'irrorder to discharge its contents when desired. The chief aim in apparatus of this kind is to ensure that every particle of aggregate receives a coating of cement, without which :theconcrete cannot be said to be properlymixed. In order 'to improve the mixing effect, it has heretofore been proposed to provide the drum with vanes, ribs or .projections, 'but none of these prior proposals, so far as known, has yet resulted in a sufiiciently efiic'ient mixing.

It is, 'therefore, an object ofthe invention to provided a new and improved mixing drum that shall-mixtogether-the ingredients which form the concrete or the like more efficiently than heretobe'fore in a :reasonably short time and by a smooth motion which avoids jarring and strain upon the machine. A further objector aim is to provide uppar-atus that shall be simple .inconstruction, economical in cost, and inexpensive to run. The above objects and aims are well demonstrated in our invention, a brief description of which will now be given, with the aid of the accompanying drawings, illustrating a mixing receptacle made according to a lpreferrod form of the inventlon.

Figure 1 is a vertical section. F-igalrei2 s a perspectiveview of :the same with the upper part. removed for the purpose the lower portion, Figure 3 is an externalkperspective view taken from a position towards the rear or bottom of the receptacle.

Figure 4' is an .elevation of the interior the uppurpose looking straight i-nto' the receptacle, per part being removed for the same as in FigureQ. p

The reference letters 'W'hich are repeated in the difierent fignresdenote the same parts.

The mixing receptacle, for convenience called a dru m, is of :the known type 0011- March 24, 192 7,l*Serial *No.178,060, and in Great Britain September 28, 1926.

sisting of a short cylinder A- with a frustoconical end B, presenting an :o ening C of reduced. diameter, and closed at-it e other end by a basin-like'base D, which meets the cylindricalpart in a curve. Rising from the centre of the basinvli-ke base Dis a boss E forming the bearing for the pivot pin F on which the drum is adapted to be rotated by means of the usual outside circular rack G which is provided upon all drumsof this class. The axis ofrsuch adrumis inclined at an upward angle of twenty to thirty degrees to the horizontal or more or less, that is, so that the material which is'being mixed therein shall :not escape until the drum is tilted for discharging the contents in the usual manner. According to the specific embodimentof-the present invention that is herein illustrated and-described,-the base 1) of the drum is formed with an inclined track, and witha step connecting the high and low ends of the track,-or';portions of the track, to ether;

- he central boss E above mentioned stands up somewhat like a tapered cone, truncated or died on thesmp where thecentr'e pin F is terminated by an exposed roundv head H, the :other end of the boss merging in-a curve with the base iD, avoiding a sharp angle at the junction. To understand the invention, one may now imagine the interior of the base D to be bisected by a plane passing through the axis, dividing the base, therefore, on a diametric line. A'sudden' step or depression J is wprovided-by suitably shaping the base-mlong each of the two :radial lines (where this diametrical division occurs) on either side of the central boss E, and the surface of the base D rises, in an inclined path K from the depression at one radial line until the opposite radial line is reached where another similar drop or step J occurs. Expressed difierently, the surface of the interior of the base is divided into 'two-.-semi-circulair tracks or half-circuits K K, each half K resembling the ihal f-of one cnil oflakhelix made oZE flat ribbon which ribbon may however be curved or otherwise shaped infcross sectional View if desired. The upward terminal edge off each track K is broader than the lower'end or root, as the latter necessarily lies in'the restricted depth of the base I) which gradually widens wardl. to its. maximum at, cylidica'l portion Aiioffthe drum. Such details of design, however, may not be material. It isessential to provide the steps or sudden depressions J such as above men tioned for the. following reason. The ingredients get carried for only a small dis-. tance against gravity upon each inclined track K as the drum rotates counter-clockwise (as viewed in Fig. 4.), the material continuously rolling and falling over the surfaces of the tracks K K. It is necessary that the material shall not travel upwards to any height. The early. falling is the most important result to aim at, whereby the material describes a practically continuous movement, as one incline immediately follows the other, with a step in between. The inclination of each track K becomes steeper in relation to the vertical as it travels higheuand overhangs somewhat when it is at the highest point, as seen in the section K, Fig. 1. This prevents the material from rising into the drum any distance, and so entirely overcomes separation of the large and small particles. The material is continuously turned over, the action closely reseinbling a kneading motion in which gravity is the chief factor.

' The centre boss E acts as a divider or de fiector when the charge is so increased as to cause the volume of the wave to reach this height in the drum. In some cases, one track could be used instead of-two and in such a case only one step J would be re quired. A pair of helical or equivalent do flectors L (one only shown Fig. 1 is provided,these being set in an opposite direction higher up in the drum to compel the material, when a large fall back again into the heart of the mix and become agitated over again.

The interior formation above described is. shown on the drawings as if made by press ing the metal ofthe base into the desired shape, visible also from the outside, a-s-seen clearly in Fig. 3. If preferred,'-the number of steps or depressions J can be increased beyond. the two specified. Also they can be made otherwise than by pressing, if desired, as will be easily understood.

We claim: Y

1. In a mixing machine, a rotary mixing receptacle or ing of reduced diameter and closed at the having a boss at its centre forming a hearing on which the drum may rotate, the interior of the base essentially being in the form of an inclined track and with a step to connect the high and low ends of the. same for the purpose specified.

2. In a mixing machine, a drum as claimed in claim 1 of which the base is formed by the operation of pressing or stamping.

3. In a mixing machine, a rotary mixing between the axis and the walls and batch is treated, to

a step,

drum having a frusto-conical' terminatlon presenting at one end an open-.

the latter drum having a base and an open top and walls connecting the base with the top, means for rotating the drum about an axis disposed longitudinally of the drum the drum being provided with a track disposed having one or more portions that extend substantially spirally about the axis, whereby one of the ends of the track is disposed nearer the open top than is the other end, the track having a portion connecting the ends together to form a step.

4. In a mixing machine, a rotary mixing drum having abase and an open top and walls connecting the base with the top, means for rotating the drum about an axis disposed longitudinally of the drum, the drum being provided with a trackdisposed between the axis and the walls and having a plurality of portions each extending substantially S )1121lly about the axis, whereby one of the ends of each portion is disposed nearer the open top than is its other end, the track having a portion connecting the said one end of one portion to the said other end of another portion to form a step.

5. In ainixing machine, a rotary mixing drum having a base and an open top and walls connecting the base *ith the top, means for rotating the drum about an axis disposed longitudinally of the drum, the drum beii'ig provided with a track disposed between the axis and the walls and having one or more portions that extend substantially spirally about the axis, whereby one of the ends of the track is disposed nearer the open top than is the other end, the track having a portion connecting the ends together to form and the track being connected throughout to the walls.

6. In a mixing machine, a rotary mixing drum having a base and an open top and walls connecting the base with the top, the base having a bearing projecting interiorly into the drum longitudinally of the drum, a pin being adapted to extend into the bearing, means'for rotating the drum about the pin, the walls tapering toward the axis of rotation in the neighborhood of the open top, whereby the cross dimension of the open top is less than the cross dimension of other parts of the drum, the drum being provided with a track disposed between the bearing: and the walls and having one or more portions that extend substantially spirally about the bearing, whereby one of the ends of the track is disposed nearer the open top than is the other end, the track having aportion connecting the ends along the-walls and the bearing to form a longitudinally extending step, and the track being connected throughout to the walls and the bearing.

7. In a mixing'machine, a rotary mixing drum having a basin-shaped base and a frusto-conical open top and walls connecting the base with the larger diameter of the frusto-- conical top whereby the opening at the top is of reduced diameter, the base having a centrally disposed bearing projecting interiorly into the drum longitudinally of the drum, a pin being adapted to extend into the bearing, means for rotating the drum about the pin, the base being interiorly shaped to constitute a track extending substantially spirally about the bearing between the bearing and the walls, whereby one end of the track is disposed nearer the open top than is the other end, the track having a portion connecting the ends to form a longitudinally extending step.

8. In a .mixing machine, a rotary mixing drum having a basin-shaped base and a frusto-conical open top and walls connecting the base with the larger diameter of the frusto-conical top, whereby the opening at the top is of reduced diameter, the base having a centrally disposed bearing projecting interiorly into the drum longitudinally of the drum, a pin being adapted to extend into the bearing, means for rotating the drum about the pin, the base being interiorly shaped to constitute a track having a plurality of portions each extending substantially spirally about the bearing between the bearing and the walls, whereby one of the ends of each portion is disposed nearer the open top than is its other end, the track haw ing portions connecting the said one endof each portion with the said other end of each adjacent portion to form longitudinally extending steps between the portions.

9; In a mixing machine, a drum having a body portion and a frusto conical upper portion the walls of which taper from the body portion towards the top of the drum, the drum being open at the top only, whereby the opening at the top is of reduced diameter, the body portion having a bearing member projecting interiorly into the drum longitudinally of the drum, the drum being adapted to be positioned with the bearing member at an incline to the horizontal and being constructed and arranged to be rotated about the inclined bearing member, and the drum being provided with a track extending around the bearing member and having one or more portions inclined with respect to the bearing member and connected together at their extremities by one or more steps.

10. In a mixing machine, a drum as claimed in claim 9 in which the one or more inclined portions of the track and the one or more steps together extend continuously completely around the bearing.

11. In a mixing machine, a drum as claimed in claim 1 in which the surface of the track is curved in cross section.

In witness whereof we have signed this specification.

J. FAULDER BURN. JOHN LANCASTER. 

